It is already standard practice to provide safety harness for use by anyone on the deck of a boat, particularly a sailing craft. By means of a lanyard and hooks one can be clipped to secure points of the craft or specially rigged lifelines. This is not entirely satisfactory since movement about the deck is thereby considerably restricted, thus discouraging use of the equipment; danger exists whilst moving the attaching hook or clip from point to point and "strong" points in craft are prone to failure under stress.
It is also known to install a guard rail system of wires and stanchions around the periphery of boats decks in order to help obstruct falls overboard. However these systems provide only a modest degree of security because of inherent boat design limitations.
Given such fallible existing arrangements a boat has to be put about in order to recover a person who does fall overboard. This manoeuvre, particularly under sail, often presents extreme difficulty and is sometimes impossible in heavy weather, and is of course out of the question in a single-handed craft. Even if the manoeuvre is completed the task of hauling a person back into the boat in waterlogged clothing and perhaps unconscious will often present considerable difficulties.